SJAA

Ephemeris

The Shallow Sky

Akkana Peck


February should have some lovely planet groupings in the western sky at sunset (more on that later), but the big news is Mars.

This month marks the real beginning of Mars' 1999 apparition. During February, Mars will double in brightness, and by month's end it will show a disk 10" across, nearly one third the size of Jupiter. Start exercising your "Mars eyes" now, getting practice in identifying the features, so that you'll be ready to see all the detail you can when the planet reaches opposition just two months from now. By now, quite a few features such as the north polar cap, Hellas, Syrtis Major, and more should be visible through a small telescope. It's high summer on the northern hemisphere of Mars (the solstice was January 29), so the north polar cap should be shrinking; can you see it change over a period of a few weeks? Ambitious planetary observers might want to look for orographic clouds over the Tharsis volcanos; use a violet or blue-green filter, and compare with an unfiltered view.

You can get more information on observing Mars at the ALPO Mars site: http://www.lpl.arizona.edu/~rhill/alpo/marstuff/marsapp.html

One challenge of observing Mars is the difficulty of keeping track of the planet's rotation combined with its orientation in the telescope eyepiece. It's easy to get lost and not know which feature you're looking at (is that white spot the polar cap, or Hellas on the limb?) A computer program can help -- some programs (Guide, for one) calculate the planet's rotation and show features in their correct orientation. In the absence of a computer, I've found a Mars globe much more useful than a static map. The best globe I've seen is made by Replogle and comes in a set of three (the other two are the earth and moon) for a very reasonable price when you can find it at all; I found mine at the children's store in the Great Mall.

Moving on to other planets:

Saturn still shines high in the evening sky. It's not too late to get a good look at the ringed planet. The rings are still opening, and we'll get an even better show next time around than we did this time.

Venus continues the excellent show it gave last month, starting low in the evening sky but gaining altitude rapidly to catch up with Jupiter around the evening of February 23, when they are only 11' apart (less than half the moon's diameter). Its phase is gibbous.

This may be the last month for a while to get a good look at Jupiter, which is already getting low at sunset. It makes a nice grouping with Venus, the two brightest planets competing for our attention in the early evening sky.

Mercury, too, has returned to the evening sky. At mid-month, it will shine at magnitude -1 low in the sunset sky; but by the end of February the planet will be near its peak elevation for this apparition, and showing just slightly more than 50% of its disk illuminated. On February 16, use binoculars to try spotting Mercury just above a very young crescent moon.

Uranus and Neptune are close to the sun and are not observable this month.

Pluto is about to cross Neptune's orbit to regain its place as the farthest planet from the sun, which will happen on February 11th at 2:08am. This is your last chance for 230 years to see "Planet X" as the eighth rather than the ninth planet from the sun. Unfortunately, it's still quite close to the sun, so expect quite a challenge in identifying it.

Asteroid 4 Vesta reaches opposition in eastern Cancer on February 4th. It will be magnitude 6.2, possibly barely visible with the naked eye from a dark site such as Fremont Peak or Coe, and should be an easy target in binoculars.


Akkana Peck; last updated: 1999 Jan 18 Prev Next